Sewer Skip is a boost jump over Garam's dialogue trigger. This trigger is also what spawns the gate that blocks off Bottom Point - skipping the trigger means the gate never spawns, and you can skate right to the Poison Jam fight without spraying the switches, saving almost 5 minutes.
This trick is only possible on the English Combo Disk version of JSRF. To do this on other versions, you must have the cache of the Combo Disk Sewers saved to your harddrive before playing on the other version. Read more about how the cache works here.
To do this trick, complete Garam's tutorial so that he throws down the girders. Then, grind up the girder and boost jump at the very end of it, then hold right immediately after the jump to curve around the wall (do not jump while holding right, this will not work). If done correctly, Garam will not talk to you, and the cutscene spawning the gate will not occur, allowing free passage into Bottom Point.
The most common way of failing this is getting caught on the wall as you're jumping - this will waste your horizontal momentum and you'll land right inside the trigger. Make sure you hold right after you jump, so you get the full distance that you need. If you're still not making it, you may be holding right too late, making your curve too wide to achieve the proper distance.
Reminder that Garam's trigger is still active until you beat Poison Jam in Bottom Point. Do not skate back into it, or you'll be stuck doing Sewers.
With an extremely precise kiss the rail on the edge of the halfpipe rail, you can clip through the halfpipe and death warp beyond the entrance pit, eliminating the need to complete Garam's tutorial, or to interact with Garam at all. Unlike Sewer Skip, this trick works on all versions of the game.
You have enough time for a few attempts before Garam triggers and you're locked into his tutorial, at which point you would do the classic Sewer Skip (above).
Prior to July 2020, it had only been replicated once, until Naestrinus found a more consistent strat with quickturning and jumping while boosting. After much research by many people, the current method simply turns and jumps at the proper time (notably cutting out the boost and quickturn). See the Mods and Tools page for a tool to help learn and practice Cucumber.
An impractical way of skipping the sewers with low-cornering characters such as Combo.
This is an intended mechanic of the game, taught to you by Roboy and Garam. However you can also use it to jump to several levels of the Sewers with some precise angles.
The most common application of this, found by Walle Liao in February 2009, is to jump from the 2nd level of Sewers up to the central processor, and then boost from the processor to the 3rd level, without having to go through the normal transition passage.
There are also harder jumps from the ground level to the 1st level (requires the Kibo entrance to the open), and from the 3rd level to the top level by jumping up and clinging to a high rail. Characters with high grind stat will make this strat a lot easier.
Although boosting doesn't affect your speed in a halfpipe, it does for some reason give you the normal altitude boost when you jump. This makes some handplant jumps easier if you can spare the boost.
Doing 2 handplants before jumping boosts your speed by even more (though it is capped at 2). You can combine this with a boost to clear some pretty insane jumps, such as from the 3rd level of Sewers all the way up to the highest pipes at the top of the level.
The Climb is a glitchy set of wallrides you can use to go from the 2nd level to the 3rd very quickly.
Usually in the Sewers, if you wallride one of the walls into the corner of another wall, the game prevents you from wallriding into the corner infinitely by disabling the wall's wallride property. However, on one of the walls, this mechanic does not work as intended, allowing you to get frame-perfect wallrides all the way up the wall.
To perform this, it's best to use either Immortals or Love Shockers, as the setup requires extremely high cornering to be viable (you can do this with Gum but the jump is basically frame-perfect).
Grind the right side of the halfpipe, hold left and jump at the right time so you curve around the wall as close as possible without snagging it.
Wallride the left wall, jump as late as possible and veer to the right to set up the next wallride.
Wallride to the left and jump into the corner. Hold your control stick into the corner and you should do the glitchy wallrides automatically.
Once you get high enough, you must hold right so you wallride right, at which point you should be able to jump over to the 3rd level.
This is a finicky trick and sometimes it feels like you just can't get enough height out of the glitchy wallrides. Make sure you're optimizing every step of the trick as much as possible, so you can start the glitchy wallrides as high as possible - always wallride at the absolute peaks of your jumps, and jump out of your wallrides so your peaks line up with the walls.
The Alpha Climb achieves the same goal as The Climb, but without the glitchy wallrides. Slightly faster but extremely rare.
Characters with at least a certain grind stat (such as Yoyo) can actually cling to halfpipe rails through the fences of the zig zag section of the Sewers. Jumping seems to be required for this trick.
There is a way to get behind the gate blocking off FRZ as early as chapter 3, theoretically allowing access to FRZ much earlier than intended. Unfortunately, due to how mission files and chapters work, the load zone rejects you, making this trick useless unless we can figure out how to load the wrong mission file/change load zones/something like that.
(video maybe eventually)